The present application claims the benefit of priority to Applicant""s co-pending German Patent Application No. 10058163.3, filed in Germany on Nov. 22, 2000.
1. Field of the Invention
The present invention relates to a method and an apparatus for positioning radiation sources by way of hollow needles for the purpose of achieving an optimal dosage distribution during the introduction of various radiation sources in biological tissue. The method and the apparatus are particularly well suited for the treatment of prostate cancer with weak radioactive radiation sources (e.g., seeds).
2. Background of the Invention
In brachytherapy, tumour tissue is subjected to radiation from the shortest possible distance. This is accomplished, for example, with small radioactive and/or gamma-radiating sources which are inserted by way of hollow needles into the tumour tissue. Conventionally, a tumour is punctured by several hollow needles. In this particular case, two different methods of treating tumour tissue are typically employed.
According to a first method, a radiation source having a strong dosage of radiation is exposed to the tumour tissue. The radiation sources are put into the needles for a short period and are then taken out again. The radiation is discharged through the wall of the hollow needles. The treatment is repeated as required. The radiation sources have a very large half-life period in the magnitude of years.
According to a second method, a radiation source having a low dosage of radiation is exposed to the tumour tissue. The seeds are grain size and are discharged or implanted through the hollow needles into the tissue. The seeds remain in the tissue. The half-life period of these radiation sources amount to weeks and/or months and, during this period, the radiation drops below a therapeutic or harmful effect. For the treatment of the tumour tissue, for example, weak radioactive isotopes of the elements iodine, cobalt or palladium are typically applied.
In this second case, it is important, in order to achieve the greatest therapeutic benefit, that the dosage distribution be as uniform as possible and be located in the tumour tissue (e.g., prostate tissue) at a high level.
It is also important that the healthy tissue (e.g., the urethra tissue, the seminal vesicle tissue, etc.) shall not be subjected to radiation above a maximum dosage, which may cause renewed or protracted diseases of the healthy tissues.
In conventional systems, an amount of similar seeds having the same radiation dosage and half-life period are typically placed in the tumour tissue. In order tomaximize the therapeutic benefits, a software for dosage planning may be employed. The software determines the positions of the seeds in a Cartesian coordinate system relative to an extra-corporally secured perforated raster plate. In a conventional system, the perforated raster has a 5 mm clearance between the holes. The needles for the seed implantation are guided through the perforated raster in accordance with the specified details of the dosage planning software. They are inserted through the skin and healthy tissue and into the tumour tissue. For depth checking purposes, either a scale applied to the needles is adopted or a mechanical scale in addition to the needle is employed.
Conventionally, there are two basic methods for inserting the seeds. According to a first method, the insertion is performed by inserting hollow needles which are loaded up to the needle tip with a seed strand (e.g., RAPID STRAND(trademark)) made up of similarly therapeutic seeds. The seed strand is then anchored at the needle tip in the tissue and the needle is withdrawn. In this case, the seed strand remains in the tissue.
Two methods for the manufacture and the use of seed strands are typically employed. U.S. Pat. No. 5,460,592 to Langton et al. discloses a device for the manufacture and transport of seeds that are embedded in a bio-absorbable material. After an intervention planning, the strands are taken from a transport vessel and shortened to the required length before they are located in hollow needles. U.S. Pat. No. 5,938,583 to Grimm discloses a hollow needle that is particularly easy to fill and withdraw. U.S. Pat. No. 6,010,446 discloses a bio-absorbable spacer seed between the seeds that allows a time-related manufacture of seed strands.
A product description for xe2x80x9cRADIOACTIVE SEED SHUTTLExe2x80x9d of Messrs MED-TEC (P.O. Box 320, Orange City, Iowa 51041, U.S.A.) discloses a corresponding product whose mode of function, however, is not described. Furthermore, a product description for xe2x80x9cEXPRESS SEEDING CARTRIDGExe2x80x9d from the year 1999 of Messrs Indigo Medical Inc. (10123 Alliance Road, Cincinnati, Ohio, 45242) discloses a pre-loaded seed cartridge for the direct filling of a needle.
Referring back to the various methods of inserting seeds, the second conventionally employed method of inserting seeds involves the insertion of hollow needles through which individual seeds (e.g., free seeds) are later discharged at the needle tip. In this case, the individual seeds are discharged individually and manually by way of an apparatus at the needle tip. After this, the needle is withdrawn via a mechanical raster, manually in accordance with the planned seed clearance in the planning raster before the next individual seed is discharged. The individual seeds are re-loaded by way of a spring-based magazine. Such an apparatus is disclosed in U.S. Pat. No. 5,860,909.
In addition, U.S. Pat. No. 6,102,844 discloses a solution whereby the manual discharge of the seeds is fibre-optically monitored. In this case, and contrary to the method disclosed in U.S. Pat. No. 5,860,909, a revolver magazine is used which is very mechanically sophisticated. In addition, WO 00/61229 A1 discloses the taking of different seeds and/or seeds mixtures for the treatment. The position of the needle relative to a position reference block is visually illustrated in this case, as is the detection of an optimal seed deposit position. The selection of a magazine and a seed to be discharged from the revolver magazine is determined from the current position of the needle in the tissue. Furthermore, U.S. Pat. No. 5,906,574 discloses how the establishment of the connection to the treatment plan for an optimal treatment can be derived.
Conventionally, the seeds are supplied punctually at certain days of treatment upon the order of the doctor who is performing the treatment for a respective patient. The order is based on an approximate calculation of the seed requirement for the patient. The calculation is based on the estimation of the prostate volume via medical image data that has been established, typically, weeks before the actual treatment is performed. However, one problem with this estimation of the prostate volume is that the volume of the prostate can change in the time leading up to the date of treatment.
In practice, there is a considerable risk with regard to the fact that, on the day for the treatment, there are not enough similar seeds (e.g., dosage, half-life period, etc.) readily available for the patient. If there is a shortage of seeds, then the treatment has to be aborted. Unfortunately, this may only be discovered when the patient is in the state of narcosis, the prostate having been newly measured with an ultrasonic probe, and the time-related dosage planning having been carried out.
In addition, the seeds are expensive. They simply cannot be returned to a supplier and, at the present time, they cannot be used for other patients for treatment at a later date. If there are not enough seeds available, then all of the seeds are wasted because the operation cannot be performed. If there are too many seeds, then all of the non-placed seeds are wasted because they cannot be used for further treatment purposes. This is particularly disadvantageous because the very expensive palladium seeds have a short half-life period of just under 3 weeks. The inability to use various dosage values is therefore a financial disadvantage for the patient and for the doctor, and is a considerable treatment risk for the patient.
With the use of exclusively similar seeds (e.g., same dosage, same half-life period, etc.), it is not possible to achieve an optimal dosage distribution in the tissue. In particular, the continually improved early recognition diagnosis and the improved imaging process enable a more adapted dosage distribution. This could take tissue properties into consideration in order to reduce, for example, the risk of incontinence or infertility. In addition, with the known devices, a mixing of radiation sources may be possible in principle but with a very high manual effort, and would involve an unacceptably high risk for the patient.
Another disadvantage of the conventional systems is that all of the systems are designed for a purely manual operation. A changeover to an automatic mode of mixing of various seeds would be a highly complex undertaking.
Furthermore, all of the conventional systems support only the exclusive use of either individual seeds or of seed strands, not both. A simultaneous application of both methods for one patient typically requires an unjustifiable expenditure of effort.
A further disadvantage of conventional systems and methods is that the patient-specific manual mixing and filling of magazines and hollow needles involves a high health risk for the medical-technical personnel. In addition, inaccuracies and errors in communication between responsible staff for the dosage planning, the fillers and the implantologists can occur, and there is also the risk of incorrect seed implanting and incorrect treatment involved.
Compared with procedures involving the implantation of individual seeds, the pre-loading of the needles result in the loss of flexibility in the planning phase if the seed are not exactly deposited, or if they cannot be deposited, as planned. If seeds move after being deposited or if faulty handling or servicing occurs, the pre-loaded needles may negatively impact the quality of the treatment.
The objective of the present invention is to avoid the known disadvantages of the state of the art and to provide an improved method and an apparatus for the implantation of different seeds (e.g., different material, dosage, half-life period, etc.), as well as the implantation of spacer seeds in the tumour tissue, and to provide an improved method and an apparatus for the positioning of seeds, spacer seeds and stoppers in hollow needles or in devices for the seed strand production, in order to obtain an optimal dosage distribution in the tumour tissue after the seed implantation.
The method of the present invention, according to one example embodiment thereof, describes the positioning of radiation source seeds, spacer seeds and stoppers in hollow needles. Various seeds that are separately contained in magazines according to the isotope type (e.g., material, dosage, half-life period), are provided to the hollow needle. The individual magazines may be changed by means of a magazine changer. The magazine changer is located in a changer guide in a position that is perpendicular, e.g., vertical, to the direction of injection of the seeds. The location (e.g., position and orientation) of the needle is measured relative to a location reference block. An optimal seed deposit position is detected acoustically and/or visually and/or in a tactile manner. The selection of a magazine and a seed to be discharged from the magazine is derived from the current position of the needle in the tissue and from a treatment plan for a dosage distribution, which may be established in list form with details on the seed type and the x-y-z-coordinates relative to the location reference block.
The apparatus of the present invention, according to one example embodiment thereof, is configured to position radiation sources (seeds), spacer seeds and stoppers in hollow needles and to discharge the same from the hollow needles. A magazine changer pickup has a guideable magazine changer with magazines arranged in a changer guide in a position that is perpendicular, e.g., vertical, to the injection direction of the seeds. The magazines contain various seeds that are individually separated according to isotope type (e.g., material, dosage, half-life period, etc.). The magazine changer pickup indicates a needle pickup for a hollow needle onto which the magazine changer pickup is flanged by way of a snap closure. The needle can receive seeds from one of the magazines and discharge these seeds by way of a discharge device such as a discharge wire or a discharge stiletto. The magazine changer pickup is connected to a skid with a slide guide for the reproducible and exact positioning of the needle.
The method and the apparatus of the present invention may be advantageously employed for the treatment of prostate cancer with weak radioactive radiation sources (e.g., seeds).
The present invention also enables the mixing of seeds of various types such as iodine or palladium with different half-life periods and dosages. As a result, remaining seeds from previous operative processes can still be used as required. This has a cost-reducing effect. The risk for treatment stoppages before or after the administration of anesthesia resulting from lack of seeds is reduced accordingly.
In addition, the present invention enables the use of radiation sources with different half-life periods and different radiation dosages. With this method, some tissue regions can be radiated for shorter periods of time but at a higher intensity, and others can be radiated for longer periods of time but at a lower intensity, depending on which tissue therapy would appear most beneficial. With the free mixing of seeds, an optimal dosage distribution in the tissue can be planned and achieved. Side effects such as new formation of tumours or incontinence are reduced with the treatment of prostate cancer.
Furthermore, the dosage planning can be immediately corrected and adapted as well as after each seed discharge. Individual seeds in hollow needles can be used, and hollow needles can be filled time-related with different seeds. An improved treatment result is achieved because the dosage planning is constantly updated. A corresponding planning of the dosage distribution with the new system can be very easily realised.
The seeds can be mixed with stopper seeds and spacer seeds. This has the advantage that, with one needle, even larger interim spaces can be realised than without seeds and spacer seeds. Also, the applicator can be completely automated with a very minimum amount of effort.
The automated discharge of the seeds at pre-planned positions, the co-recording (protocol) and the feedback into the planning reduce the risk of incorrect treatment and increases the quality of the therapy. The error quota is reduced. Verifiable treatment results are obtained and the required concentration threshold is lowered.
Furthermore, the use of seeds with varying dosage and half-life period also simplifies the production of the seeds because, during the production itself, the actual individual seed dosage can be measured and a larger portion of the seeds from the production makes its way to the patient for treatment.
The radiation effects and the health risk for the personnel during manual filling are subsequently reduced.